Maternal and Fetal Circulating Levels of Thymosin α1 During Parturition

ABSTRACT: The thymus directs T-lymphocyte development and contributes to the maintenance of immune homeostasis, in part, through its production of peptides known as thymosins. In pregnancy, maternal serum levels of thymosin α₁ have been reported to be low at midgestation and to increase by term, suggesting that maternal levels represent fetal levels. To evaluate this further, we obtained maternal venous and newborn mixed cord blood from 90 pregnancies between 20 and 42 weeks of gestation at delivery. An ELISA was used for thymosin α assay, and analysis was by paired t test and regression. Maternal and newborn levels were independent of gestational age, but an apparent association (r = 0.51) between the two was inconclusive. Maternal levels (1,207 ± 947 pg/ml) tended to be higher than those of healthy adults (1,043 ± 576 pg/ml). Mixed umbilical cord serum levels (1,466 ± 940 pg/ml) were higher than maternal levels (P ≤ 0.005). Although maternal thymosin α levels may reflect fetal levels, immunological perturbations related to parturition appear to influence both.     

Amniotic Fluid Thymosin α1 Levels Increase During Gestation

ABSTRACT: Thymosin α₁ is one of several cytokines produced by the thymus that modulates immune function. The presence of elevated serum levels of thymosin α₁ in pregnant women and their newborns has suggested that this peptide may play a role in perinatal immunology. In this investigation, we used a microenzyme-linked immunosorbent assay to assay amniotic fluid for immunoreactive thymosin α₁ and found levels that were remarkably higher than newborn serum levels (P < 10^?4). The increase of thymosin α₁ in amniotic fluid with fetal age was natural logarithmic (r = 0.838, P < 10^?6). Thymosin α₁ in amniotic fluid may account for some of the immunologic properties of this medium.     

Role of the thymus in the generation of skin-homing αβ and γδ virgin T cells

Current models of lymphocyte traffic suggest that homing specificities of T cells to tissues such as skin are generated outside the thymus as a result of activation of naive T cells by antigen in lymph nodes. Virgin T cells are thought to home to high endothelial venules in lymph nodes, but are thought to be unable to home to extra-lymphoid tissues such as skin. We used the technique of in situ labeling of the thymus with fluorescein isothiocyanate to examine the homing specificities of authentically naive T cells in vivo, immediately after their export from the thymus. We report that homing specificities for skin as well as lymph node are imprinted on T cells inside the thymus, independent of antigen. We also show that both αβ and γδ emigrant T cells exhibit homing patterns to skin and lymph nodes which are identical to those of mature T cells. Our findings demonstrate a key role for the thymus in the induction of skin-homing specificities on T cells indicating that skin-homing specificities of T cells are not generated solely outside the thymus as a result of the activation of virgin T cells by antigen. The migration of thymic emigrants to extra-lymphoid tissues within a few hours of leaving the thymus may have implications for mechanisms of peripheral self-tolerance. This pathway provides an opportunity for direct virgin T cell interactions with self components only expressed in the periphery at a time when emigrants may be more susceptible to tolerance induction than mature circulating T cells.     

Identification of a T cell lineage-specific RNA/DNA helicase and its cell surface expression during intrathymic education of αβ and γδ T cells

Despite ubiquitous expression of the gene, RNA/DNA helicase protein was found to be expressed specifically in all cells of the T cell lineage. Interestingly, immature thymocytes that are rearranging T cell receptor (TCR) genes express the helicase strongly on the cell surface and the surface expression is terminated upon engagement of functional TCR by positively selecting ligands. This provides the first evidence that a protein that binds nucleic acids can directly contact the extracellular environment in a developmentally controlled manner. Our discovery of a novel molecular link between the cell surface and nuclear events specific for thymocytes suggests that thymic education is supervised by a previously unknown molecular mechanism, which can now be experimentally explored.     

DL4‐mediated Notch signaling is required for the development of fetal αβ and γδ T cells

T‐cell development depends upon interactions between thymocytes and thymic epithelial cells (TECs). The engagement of delta‐like 4 (DL4) on TECs by Notch1 expressed by blood‐borne BM‐derived precursors is essential for T‐cell commitment in the adult thymus. In contrast to the adult, the earliest T‐cell progenitors in the embryo originate in the fetal liver and migrate to the nonvascularized fetal thymus via chemokine signals. Within the fetal thymus, some T‐cell precursors undergo programmed TCRγ and TCRδ rearrangement and selection, giving rise to unique γδ T cells. Despite these fundamental differences between fetal and adult T‐cell lymphopoiesis, we show here that DL4‐mediated Notch signaling is essential for the development of both αβ and γδ T‐cell lineages in the embryo. Deletion of the DL4 gene in fetal TECs results in an early block in αβ T‐cell development and a dramatic reduction of all γδ T‐cell subsets in the fetal thymus. In contrast to the adult, no dramatic deviation of T‐cell precursors to alternative fates was observed in the fetal thymus in the absence of Notch signaling. Taken together, our data reveal a common requirement for DL4‐mediated Notch signaling in fetal and adult thymopoiesis.     

Changes in thymic export of γδ and αβ T cells during fetal and postnatal development

The thymus plays an essential role in the generation and selection of T cells and exports approximately 0.5–1% of thymocytes per day in young animals and considerably fewer in older animals. To date there have been no studies directly examining fetal thymic export in any species. Using the technique of intrathymic injection of fluorescein isothiocyanate, followed by an assay for green fluorescent cells in the periphery and for the expression of cell surface antigens on these cells, we have compared directly the export of T cells from the fetal and postnatal ovine thymus. While the thymus exports both αβ and γδ T cells, our results demonstrate that the proportion of thymic γδ T cells that are exported per day is much higher than that of thymic αβ T cells. Moreover, the export rate of γδ T cells increased from approximately 1 in every 60 γδ thymocytes per day emigrating from the fetal thymus to 1 in every 20 from the postnatal thymus. In addition, we identify a population of CD5⁺CD4^?CD8^?γδ^? T cells emigrating from the fetal thymus but greatly reduced among thymic emigrants after birth. These findings have several implications regarding the mechanisms and control of selection of both γδ and αβ T cells.     

Changes in thymic export of L-selectin+ γδ and αβ T cells during fetal and postnatal development

We have used the technique of in situ intrathymic injection of fluorescein isothiocyanate to examine L-selectin expression on γδ and αβ T cells immediately after emigrating from the thymus of fetal and postnatal animals. We found that the percentage of L-selectin⁺ thymocytes exported per day decreased by half after birth and that the export of T cells from the thymus does not rely on expression of the peripheral lymph node homing receptor, L-selectin. Analysis of L-selectin on emigrant and mature T cell subsets revealed a remarkable heterogeneity of expression, both in terms of the numbers of cells expressing this molecule as well as the level of expression. γδ T cells, reportedly not having a propensity for homing to lymph nodes, not only contained the highest proportion of L-selectin⁺ cells, but also expressed far more of this molecule than either CD4⁺CD8^? or CD4^?CD8⁺ αβ T cells. Furthermore, those emigrant T cells expressing L-selectin are somewhat immature in their expression of this molecule. Subsequent maturation resulted in up-regulation of L-selectin on mature peripheral blood T cells, maturation that was clearly independent of extrinsic antigen. This antigen-independent post-thymic maturation appeared to occur as part of the normal progression from immature thymocyte to mature peripheral T cell in both fetal and postnatal animals.     

CD45RA expression on γδ and αβ T cells emigrating from the fetal and postnatal thymus

We have compared the expression of CD45RA on αβ and γδ T cells emigrating from the fetal and postnatal thymus. The fetal and postnatal thymus export both CD45RA⁺ and CD45RA^- T cells. The number of γδ⁺CD45RA⁺ T cells was remarkably constant regardless of stage of ontogeny or T cell maturity. Around 5--8% of γδ thymic emigrants, thymocytes and peripheral blood lymphocytes expressed CD45RA in both fetal and postnatal animals. In contrast to γδ T cells, up to one quarter of both fetal and postnatal αβ emigrants expressed CD45RA. Post-thymic maturation of CD45RA expression on αβ emigrants, which occurred both before and after birth, appeared to be antigen independent.     

High Serum Osteopontin Levels Are Associated with Low Bone Mineral Density in Postmenopausal Women

Osteopontin (OPN) is an acidic, noncollagenous matrix protein produced by the bone and kidneys. It is reportedly involved in bone resorption and formation. We examined the association between serum OPN levels and bone mineral density in postmenopausal women. Premenopausal women (n=32) and postmenopausal women (n=409) participated in the study. We measured serum osteopontin levels and their relationships with bone mineral density and previous total fragility fractures. The postmenopausal women had higher mean serum OPN levels compared to the premenopausal women (43.6±25.9 vs 26.3±18.6 ng/mL; P<0.001). In the postmenopausal women, high serum OPN levels were negatively correlated with mean lumbar bone mineral density (BMD) (r=-0.113, P=0.023). In a stepwise multiple linear regression model, serum OPN levels were associated with BMD of the spine, femoral neck, and total hip after adjustment for age, body mass index, smoking, and physical activity in postmenopausal women. However, serum OPN levels did not differ between postmenopausal women with and without fractures. Postmenopausal women exhibit higher serum OPN levels than premenopausal women and higher serum OPN levels were associated with low BMD in postmenopausal women.     

Substitution of aspartic acid at β57 with alanine alters MHC class II peptide binding activity but not protein stability: HLA-DQ (α1*0201, β1*0302) and (α1*0201, β1*0303)

In class II major histocompatibility complex (MHC) proteins, residue β57 is usually aspartic acid. Alleles carrying serine, valine, or alanine at this position are strongly correlated with the development of insulin-dependent diabetes mellitus (IDDM). Aspβ57 participates in a conserved salt bridge that bridges the α and β subunits in the peptide-binding site. It has been proposed that the correlation between IDDM and MHC alleles lacking Aspβ57 may be due to an instability of the protein caused by loss of this salt bridge. Using a pair of HLA-DQ proteins (α1*0201, β1*0302) and (α1*0201, β1*0303) differing only in having aspartic acid or alanine at position β57, we show that the polymorphism does not have a significant effect on protein stability for either the empty or peptide-loaded forms. However, the circular dichroism spectra indicate that empty and peptide-loaded Alaβ57 proteins display slightly different secondary structures relative to their Aspβ57 counterparts. A set of three peptides shows different binding affinities for DQ(α1*0201, β1*0302) relative to DQ(α1*0201, β1*0303). We propose that substitution of Aspβ57 residue causes a local rearrangement within the DQ peptide-binding site that alters the peptide-binding specificity. This rearrangement may help to explain the previously observed differences in SDS stability between Asp and non-Aspβ57 DQ proteins.     

Intra- and extra-thymic expression of the pre-T cell receptor α gene

We have analyzed pre-T cell receptor α (pTα) gene expression in cells from various anatomical sites to investigate the lineage specificity of pTα RNA as well as its presence in pro-T cells and in sites of extrathymic T cell development. pTα RNA is found in precursors of αβ T cells but is absent from mature αβ T cells as well as T cells that express the γδ T cell receptor on the cell surface. pTα expression is exquisitely T lineage specific in that mature and immature B cells, myeloid cells, NK cells and pluripotent stem cells are pTα negative. On the other hand, pTα expression is found in pro-T cells outside the thymus as well as in intra- and extra-thymic sites of T cell development. The latter finding is consistent with the notion that early steps of T cell development within and outside the thymus may be similar.     

The homogeneity of the TCRδ repertoire expressed by the Thy-1dull γ δ T cell population is due to cellular selection

Thy-1^dull γ δ T cells are an unusual subset of mature TCRγ δ T cells characterized by their highly restricted TCR repertoire. In DBA/2 mice, they predominantly express the product of the Vγ1 gene together with that of a member of the Vδ6 subfamily (the Vδ6.4 gene) and their junctional sequences show very little diversity. To address the mechanisms underlying the expression of the restricted TCRγ δ repertoire, we have cloned all Vδ6 subfamily members present in DBA/2 mice and studied their frequency of expression in Thy-1^dull and Thy-1^bright γ δ thymocyte populations. Furthermore, we have also cloned non-functional Vδ6DδJδ1 rearrangements present in the Thy-1^dull γ δ T cell population and compared their Vδ6 gene utilization and their junctional sequences with those expressed by this population. Our results indicate that the restricted TCRδ repertoire expressed by the Thy-1^dull γ δ thymocytes results from cellular selection, rather than molecular constraints suggesting the existence of a limited set of self-ligands. Finally, phenotypic, functional and TCRγ δ repertoire analysis of Thy-1^dull γ δ T cells in β2 -microglobulin (β₂m)-deficient mice indicated that these putative ligands are not β₂m-dependent major histocompatibility complex class I or class I-like molecules.     

Impact of α-defensins1–3 on the maturation and differentiation of human monocyte-derived DCs. Concentration-dependent opposite dual effects

α-defensins1–3 are potent antimicrobial molecules that also link innate and adaptive immunity, depending on the concentration range. However, their effects on the biology of human DCs remain largely unknown. We analyzed the impact of different concentrations of α-defensins1–3 on the maturation and differentiation of monocyte-derived DCs (MDDCs). Low doses of α-defensins1–3 up-regulated CD83, CD86 and HLA-DR expression, increased TNF-α, IL-1β, IL-12p40, IL-10 and IL-8 secretion, and slightly augmented allostimulatory capacity. By contrast, high doses down-regulated CD86 and HLA-DR expression, TNF-α, IL-1β, IL-12p40 and IL-10 secretion and allostimulatory capacity, whereas strongly up-regulated IL-8. Furthermore, during the MDDC differentiation process, high doses of α-defensins1–3 affected CD14, CD11c and CD86 expression and strongly up-regulated IL-8. Results suggest that α-defensins1–3 might modulate the maturation and differentiation of MDDCs in vivo and therefore could be of special interest in the field of vaccine development.     

Stepwise Synthesis of γ‐Glutamic Acid 16‐Mer

γ‐Glutamic acid 16‐mer α‐ethyl ester was synthesized in stepwise transesterification of the ethyl ester group into benzyl ester group, followed by hydrogenation afforded γ‐glutamic acid 16‐mer with free carboxyl groups. Alkaline hydrolysis of γ‐glutamic acid 16‐mer α‐ethyl ester also afforded 16‐mer with free carboxyl groups. The two 16‐mers showed similar circular dichroism spectra. The structures and optical properties of γ‐glutamic acid dimer, trimer, tetramer, octamer, and 16‐mer were elucidated by ¹H NMR, ¹³C NMR, IR, circular dichroism spectra, and X‐ray. Specific rotation of the intermediates of 16‐mer increased as the number of the glutamate unit.     

Maternal Blood Serum and Plasma Human Tumor‐Associated Antigen RCAS1 During the Course of Uncomplicated Pregnancies: A Prospective Study

Citation Tskitishvili E, Sharentuya N, Tsubouchi H, Kinugasa‐Taniguchi Y, Kanagawa T, Shimoya K, Tomimatsu T, Kimura T. Maternal blood serum and plasma human tumor‐associated antigen RCAS1 during the course of uncomplicated pregnancies: a prospective study. Am J Reprod Immunol 2010; 64: 218–224 Problem We aimed to investigate the expression of the tumor‐associated RCAS1 protein in maternal blood of uncomplicated pregnancies. Method of study Maternal blood was obtained from women with uncomplicated pregnancies (N = 43) at 11–13, 20–22, 32–34, 37–38 weeks of gestation, and immediately after delivery. Serum RCAS1 concentration was studied by ELISA, and plasma mRNA was subjected to real‐time (RT)‐PCR. Results Serum RCAS1 protein concentration was significantly up‐regulated at 11–13 and 20–22 weeks than that at 32–34 weeks and after delivery. RCAS1 mRNA level was significantly increased at 11–13 weeks than that at 37–38 weeks. A significant positive correlation was defined between RCAS1 serum concentration at 11–13 weeks and gestational age at delivery and that between plasma RCAS1 mRNA levels at 37–38 weeks and umbilical cord blood base excess. A significant negative correlation was found between RCAS1 serum concentration at 37–38 weeks and umbilical cord blood pH at delivery. Conclusions RCAS1 protein might have importance in the development of uncomplicated pregnancies and for the prediction of pregnancy outcome.     

Transendothelial chemotaxis of human αβ and γδ T lymphocytes to chemokines

Two subpopulations of human T lymphocytes expressing different antigen receptors, α / β and γ / δ, emigrate into inflamed tissues in distinctive patterns. We compared the transmigration of α / β and γ / δ T cells to C-C and C-X-C chemokines using an in vitro transendothelial chemotaxis assay. The C-C chemokines monocyte chemoattractant protein (MCP)-1, RANTES, macrophage inflammatory protein (MIP)-1α and MIP-1β stimulated similar, dose-dependent chemotaxis of purified γ / δ T cells, whereas MCP-1, RANTES, and MIP-1α pro duced greater chemotaxis of purified α / β T cells than MIP-1β. In contrast, the C-X-C chemokines interleukin (IL)-8 and interferon-γ inducible protein-10 (IP-10) did not promote chemotaxis of either α / β or γ / δ T cells. Three γ / δ T cell clones with differing CD4 and CD8 phenotypes also migrated exclusively to C-C chemokines. Phenotypic analysis of mononuclear cells that transmigrated from an input population of unfractionated peripheral blood mono nuclear cells confirmed the results with purified γ / δ T cells. Our data demonstrate that human peripheral blood α / β and γ / δ T cells can transmigrate to MCP-1, RANTES, MIP-1α, and MIP-1β, and suggest that both T lymphocyte subpopulations share the capacity to emigrate in response to C-C chemokines during inflammation.     

Increased Plasma Thrombospondin-1 (TSP-1) Levels Are Associated with the TNFα-308A Allele in Children with Juvenile Dermatomyositis

Vascular occlusion is more frequent in children with juvenile dermatomyositis (JDM) who have the TNFα-308A allele. One of the potent anti-angiogenic factors is thrombospondin-1 (TSP-1). This study investigated the association of the TNFα-308A allele with circulating levels of angiogenic mediators, TSP-1, and platelet factor 4 (PF4) using fresh, platelet-poor plasma (PPP). The TNFα-308A allele was characterized by PCR amplification and NcoI digestion. Concentrations of TSP-1 and PF4 in PPP from 31 JDM patients and 25 matched pediatric controls were determined by ELISA. The majority of the JDM children with the TNFα-308A allele (7/12) produced more TSP-1 than their TNFα-308G counterparts (P < 0.05), and their TSP-1 values were inversely related to those for PF4 (P < 0.0006). We conclude that the increased circulating concentrations of TSP-1 associated with the TNFα-308A allele suggest that this anti-angiogenic regulator may play a significant role in the augmented vascular occlusion observed in JDM children with this genetic marker.     

Developmental expression of the αIELβ7 integrin on T cell receptor γδ and T cell receptor αβ T cells

A novel monoclonal antibody, 2E7, was shown by immunoprecipitation to be reactive with the α_IELβ7 integrin and was employed to analyze the expression of this integrin in lymphocyte subsets and during T cell ontogeny. In adult lymph nodes, α_IEL was expressed at low levels by 40–70% of CD8⁺ T cells and < 5% of CD4⁺ T cells. However, virtually all intestinal intraepithelial lymphocytes and ?20% of lamina propria CD4⁺ T cells were 2E7⁺, indicating a preferential expression of this integrin on mucosal T cells. Examination of α_IEL integrin expression during thymus ontogeny revealed that ?3–5% of fetal or adult thymocytes were 2E7⁺. Interestingly, early in fetal thymus ontogeny, ?40% of 2E7⁺ cells expressed T cell receptor (TcR)-γδ and this subset persisted through birth. A developmental switch occurred such that 2E7⁺ TcR^? CD4^?8⁺ cells detected on fetal day 19 were followed by 2E7⁺ TcR-αβ CD4^?8⁺ cells in the neonatal thymus. The latter population persisted throughout thymus ontogeny into adulthood. Interestingly, a subset of TcR-γδ Vγ3⁺ day 16 fetal thymocyte dendritic epidermal cell (DEC) precursors were 2E7⁺, but all mature DEC expressed high levels of α_IEL integrin, suggesting that the α_IEL integrin was acquired late in DEC maturation. This possibility was strenghthened by immunohistochemical localization of the majority of 2E7⁺ γδ and αβ T cells to the medullary regions of the thymus. Overall, the results demonstrate a developmentally ordered expression pattern of the α_IELβ₇ integrin that suggests a common function for this integrin during TcR-γδ and -αβ CD4^?8⁺ T cell thymocyte development or perhaps in effector functions for these subsets.